1. Field of the Invention
The present invention relates generally to a multi-grade object sorting system and method and more particularly to such a system for sorting various grades and colors of paper.
2. Description of the Prior Art
The high speed sorting of waste paper has only recently become feasible with the introduction of a system by the Assignee of the present invention as described in pending U.S. patent application Ser. No. 09/301,715, filed Apr. 29, 1999, entitled “System and Method for Sensing White Paper”, by Bruner et al., the details of which are incorporated herein by reference. The first such system as described in the aforementioned application, could only identify and separate white office paper. The technique utilized for identifying and distinguishing such paper was the presence of the fluorescence of the paper when subjected to ultraviolet light.
It has been proposed to sort paper based on color as described in European Patent Publication No. EP0873797A2, published on Oct. 28, 1998. The European patent publication proposed to utilize visible light, ultraviolet light, x-rays and/or infrared light to illuminate the paper, while observing the reflected light with one or more cameras connected to a central processing unit. The disclosure of the European patent office publication is very vague with regard to the manner in which such a process could be conducted, and its sorting system utilizes mechanical pickers thus indicating that the system would operate at relatively low speeds.
Sorting systems for other objects other than paper are available which utilize red, green and blue light emitting diodes as light sources. An example is a product sold by the Assignee of the present invention is described in pending U.S. patent application Ser. No. 09/183,349 filed Oct. 30, 1998 by Doak, the details of which are incorporated herein by reference.
Thus, it is seen that there is a need for a system capable of sorting paper based upon the color of the paper, and capable of doing so at sufficiently high speeds as to make the process economical. Such a system, along with various refinements thereof is the subject of the present invention.